Unlike a monogastric animal such as a human and others, a ruminant animal such as cattle etc. has a plurality of stomach compartments, with the first compartment (i.e., the rumen) being resided by a large population of microorganisms. A natural process is called a rumination when rumen contents are regurgitated to the mouth, and then salivated, masticated, and swallowed back. In view of such rumination, when a biologically active substance contained in feed without any pre-treatment is orally administered to ruminants, a majority of such substance will only be attacked and broken down by the rumen microorganisms. For example, when a biologically active substance such as a vitamin, an amino acid, and the like is administered to cattle, most of the substance is attacked and broken down by the microorganisms residing in the rumen, resulting in loss without effective digestion and absorption. When the biologically active substance is prepared in the form of a rumen bypass product to be protected from attack and breakdown by the rumen microorganisms for effective digestion and absorption in the abomasal and postabomasal digestive tract (i.e., the abomasum and the small intestine), such biologically active substance can serve as a very useful nutrient agent etc.
Conventionally, rumen bypass products have long been utilized, by dispersing a biologically active substance in a protective material such as wax, animal and vegetable fats and oils or their hardened materials, or by coating a core which contains a biologically active substance. For example, methods of dispersing a biologically active substance in a protective material have been developed, such as a method of granulating through blending a biologically active substance with a protective material (refer to Unexamined Japanese Patent Application (Kokai) No. 1985-168351 (Patent Reference 1)), or a method of granulating through melting, in which a melt liquid with a biologically active substance being blended and suspended in a molten protective material is dropped onto a belt (refer to Unexamined Japanese Patent Application (Kokai) No. 1983-175449 (Patent Reference 2)).
Alternatively, by way of coating a biologically active substance with a protective material, there is a method developed for forming a core that contains a biologically active substance and then coating the core with a protective material (refer to Unexamined Japanese Patent Application (Kokai) Nos. 1988-317053 and 1993-23114 (Patent Reference 3 and 4)).